The present invention relates to a rotation transmission device mounted in a power train of a vehicle for selectively permitting and prohibiting torque transfer.
Such a rotation transmission device is disclosed in unexamined JP patent publication 2001-165197. The rotation transmission device disclosed in this publication includes an inner shaft as an input member, an intermediate shaft provided around the inner shaft, and an outer shaft as an output member provided around the intermediate shaft. A two-way clutch and an electromagnetic clutch for selectively engaging and disengaging the two-way clutch are mounted between the inner shaft and the intermediate shaft, and another similar clutch pair is mounted between the intermediate shaft and the outer shaft.
The two-way clutch mounted between the inner shaft and the intermediate shaft comprises a cam non-rotatably mounted on the inner shaft and formed with a plurality of cam surfaces on its outer periphery, a plurality of rollers each received in a wedge-shaped space defined between a cylindrical surface formed on the inner periphery of the intermediate shaft and one of the cam surfaces, a retainer for retaining the rollers, and a switch spring for elastically biasing the retainer toward its neutral position where the rollers are not in engagement with at least either the cylindrical surface or the cam surfaces.
The two-way clutch mounted between the intermediate shaft and the outer shaft comprises a plurality of rollers each received in a wedge-shaped space defined between a cylindrical surface formed on the inner periphery of the outer shaft and cam surfaces formed on the outer periphery of the intermediate shaft, a retainer for retaining the rollers, and a switch spring for elastically biasing the retainer toward its neutral position where the rollers are not in engagement with at least either the cylindrical surface or the cam surfaces.
The electromagnetic clutches mounted between the inner shaft and the intermediate shaft and between the intermediate shaft and the outer shaft are of the same structure and each comprise an armature coupled to the retainer of the two-way clutch so as to be non-rotatable but axially movable relative to the retainer, a rotor axially fixed to the outer one of the two shafts between which the electromagnetic clutch is mounted so as to axially face the armature, and an electromagnet axially facing the armature with the rotor disposed therebetween. By energizing the electromagnet, the armature is attracted toward the electromagnet until it is pressed against the rotor. The retainer thus rotates relative to the inner one of the two shafts. The two-way clutch thus engages.
Another conventional rotation transmission device includes an input shaft, an outer ring as an output member provided around the input shaft, and a two-way clutch and an electromagnetic clutch similar to the above-mentioned clutch pair and mounted between the input shaft and the outer ring.
In any of these conventional rotation transmission devices, it is necessary to lubricate its two-way clutch or clutches. One way to lubricate such a two-way clutch would be to seal grease in the device. But because the components of the rotation transmission device rotate at high speeds, the sealed grease tends to move radially outwardly under centrifugal force and leak from the device. The grease is thus lost soon, leaving the two-way clutches unlubricated. Thus, such a two-way clutch is typically lubricated by supplying oil through an oil supply passage formed in the input member into the space between the two-way clutch and the electromagnetic clutch.
In this arrangement, oil tends to be supplied into the space between the two-way clutch and the electromagnetic clutch at a higher rate than the rate at which oil is discharged from this space. Thus, the pressure of oil in this space tends to rise. Increased oil pressure in this space may act to move the armature toward the rotor and actually press the former against the latter when the electromagnet is not energized, thus undesirably engaging the two-way clutch. Conversely, while the electromagnet is being energized, increased oil pressure in the space between the two clutches may act to push the armature away from the rotor against the magnetic force produced by the electromagnet. This may cause the two-way clutch to be disengaged in an untimely manner for a short period of time. In either case, the two-way clutch cannot be controlled in a stable and reliable manner.
An object of the present invention is to provide a rotation transmission device having means for preventing a rise in oil pressure in the device, thereby preventing the armature of the electromagnetic clutch from being pressed against or separated from the rotor.